1. Field of the Invention
This invention relates to an apparatus for removing foreign substances such as water droplets, ice and frost, for example, from a surface.
2. Description of the Related Art
Japanese utility model laid-open patent No. 61-30552, published on Feb. 24, 1986, discloses a conventional apparatus of the above-described type.
FIG. 5 is a cross-sectional view of the conventional apparatus which is adapted to an automotive rear-view mirror 72. A mirror 71 is supported by a stay or support 73 via a vibrator 74. An oscillator 76 is electrically connected to the vibrator 74. A switch 75 is electrically connected between a battery 77 and the oscillator 76. The switch 75 is disposed in a compartment of the automobile so as to be easily accessible by a driver or passenger of the automobile.
When the switch 75 is turn on, the vibrator 74 vibrates the mirror 71. The vibration of the mirror 74 quickly removes foreign substances, such as water droplets, ice and frost.
However, the vibrator 74 may generate a radio wavelength noise, because an A.C. signal having high voltage and high frequency is supplied to the vibrator 74 from the oscillator 76. The radio noise may undesirably interfere with other electronic devices.
Another apparatus which is quite similar to the above conventional apparatus is disclosed in U.S. Pat. No. 4,833,373 published on May 23, 1989. A corresponding application of this U.S. Patent is disclosed in Japanese laid-open patent No. 62-238149 published on Oct. 19, 1987.